37,892 research outputs found
Asymptotics for penalized additive B-spline regression
This paper is concerned with asymptotic theory for penalized spline estimator
in bivariate additive model. The focus of this paper is put upon the penalized
spline estimator obtained by the backfitting algorithm. The convergence of the
algorithm as well as the uniqueness of its solution are shown. The asymptotic
bias and variance of penalized spline estimator are derived by an efficient use
of the asymptotic results for the penalized spline estimator in marginal
univariate model. Asymptotic normality of estimator is also developed, by which
an approximate confidence interval can be obtained. Some numerical experiments
confirming theoretical results are provided.Comment: 24 pages, 6 figure
Constraints on the origin of the ultra-high energy cosmic-rays using cosmic diffuse neutrino flux limits: An analytical approach
Astrophysical neutrinos are expected to be produced in the interactions of
ultra-high energy cosmic-rays with surrounding photons. The fluxes of the
astrophysical neutrinos are highly dependent on the characteristics of the
cosmic-ray sources, such as their cosmological distributions. We study possible
constraints on the properties of cosmic-ray sources in a model-independent way
using experimentally obtained diffuse neutrino flux above 100 PeV. The
semi-analytic formula is derived to estimate the cosmogenic neutrino fluxes as
functions of source evolution parameter and source extension in redshift. The
obtained formula converts the upper-limits on the neutrino fluxes into the
constraints on the cosmic-ray sources. It is found that the recently obtained
upper-limit on the cosmogenic neutrinos by IceCube constrains the scenarios
with strongly evolving ultra-high energy cosmic-ray sources, and the future
limits from an 1 km^3 scale detector are able to further constrain the
ultra-high energy cosmic-rays sources with evolutions comparable to the cosmic
star formation rate.Comment: 9 pages, 3 figures and 1 table. Accepted by Phys. Rev.
A model study of cooperative binding of ionic surfactants to oppositely charged flexible polyions
A novel statistical model for the cooperative binding of monomeric ligands to
a linear lattice is developed to study the interaction of ionic surfactant
molecules with flexible polyion chain in dilute solution. Electrostatic binding
of a ligand to a site on the polyion and hydrophobic associations between the
neighboring bound ligands are assumed to be stochastic processes. Ligand
association separated by several lattice points within defined width is
introduced for the flexible polyion. Model calculations by the Monte Carlo
method are carried out to investigate the binding behavior. The hypothesis on
the ligand association and its width on the chain are of importance in
determining critical aggregation concentration and binding isotherm. The
results are reasonable for the interpretations of several surfactant-flexible
polyion binding experiments. The implications of the approach are presented and
discussed.Comment: 11 pages, 9 figure
Statistical Analysis of Spectral Line Candidates in Gamma-Ray Burst GRB870303
The Ginga data for the gamma-ray burst GRB870303 exhibit low-energy dips in
two temporally distinct spectra, denoted S1 and S2. S1, spanning 4 s, exhibits
a single line candidate at ~ 20 keV, while S2, spanning 9 s, exhibits
apparently harmonically spaced line candidates at ~ 20 and 40 keV. We evaluate
the statistical evidence for these lines, using phenomenological continuum and
line models which in their details are independent of the distance scale to
gamma-ray bursts. We employ the methodologies based on both frequentist and
Bayesian statistical inference that we develop in Freeman et al. (1999b). These
methodologies utilize the information present in the data to select the
simplest model that adequately describes the data from among a wide range of
continuum and continuum-plus-line(s) models. This ensures that the chosen model
does not include free parameters that the data deem unnecessary and that would
act to reduce the frequentist significance and Bayesian odds of the
continuum-plus-line(s) model. We calculate the significance of the
continuum-plus-line(s) models using the Chi-Square Maximum Likelihood Ratio
test. We describe a parametrization of the exponentiated Gaussian absorption
line shape that makes the probability surface in parameter space
better-behaved, allowing us to estimate analytically the Bayesian odds. The
significance of the continuum-plus-line models requested by the S1 and S2 data
are 3.6 x 10^-5 and 1.7 x 10^-4 respectively, with the odds favoring them being
114:1 and 7:1. We also apply our methodology to the combined (S1+S2) data. The
significance of the continuum-plus-lines model requested by the combined data
is 4.2 x 10^-8, with the odds favoring it being 40,300:1.Comment: LaTeX2e (aastex.cls included); 41 pages text, 10 figures (on 11
pages); accepted by ApJ (to be published 1 Nov 1999, v. 525
Atomically straight steps on vicinal Si (111) surfaces prepared by step-parallel current in the kink-up direction
We demonstrate that annealing of a vicinal Si(111) surface at about 800 C
with a direct current in the direction that ascends the kinks enhances the
formation of atomically straight step edges over micrometer lengths, while
annealing with a current in the opposite direction does not. Every straight
step edge has the same atomic configuration U(2,0), which is useful as a
template for the formation of a variety of nanostructures. A phenomenological
model based on electromigration of charged mobile atoms explains the observed
current-polarity dependent behavior.Comment: Accepted for publication in Appl. Phys. Lett. Numbers of pages and
figures are 12 and 4, respectivel
Symplectic structure and monopole strength in 12C
The relation between the monopole transition strength and existence of
cluster structure in the excited states is discussed based on an algebraic
cluster model. The structure of C is studied with a 3 model, and
the wave function for the relative motions between clusters are
described by the symplectic algebra , which corresponds to the
linear combinations of states with different multiplicities.
Introducing algebra works well for reducing the number of the basis
states, and it is also shown that states connected by the strong monopole
transition are classified by a quantum number of the
algebra.Comment: Phys. Rev. C in pres
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